Conventional safety boots and safety shoes are comprised of a puncture-resistant insole which provides protection against sharp objects injuring the bottom of the foot, and a separate safety toe which provides impact protection for the toes.
The conventional puncture-resistant insole typically comprises a semi-rigid stainless steel plate, approximately 0.5 mm thick. However, due to the difficulty of bonding the stainless steel plate to the safety boot or safety shoe, the plate is usually incorporated into an insole assembly or a midsole assembly. Since the steel plate in such assemblies must be smaller than the insole of the shoe, the conventional puncture-resistant insole does not provide full protection for the underside of the foot. In addition, as the steel plate extends over a large area of the entire insole/midsole assembly, safety footwear fabricated with steel plates are excessively heavy and insufficiently flexible to allow the wearer to walk comfortably.
The conventional safety toe is typically fabricated from hardened steel. Although such safety toes provide adequate impact protection for the toes, they are excessively heavy and suffer from the disadvantage that they are perceived to contribute to cold feet. Furthermore, as steel is difficult to bond to, it has been difficult to secure the safety toe to the puncture-resistant insole in a manner which provides seamless protection for the toes and the underside of the foot.
U.S. Pat. No. 5,285,583 to Aleven teaches a safety insole which attempts to overcome some of these deficiencies. Aleven teaches a safety insole comprising a high impact-resistant plastic injection layer injection molded between an upper liner and lower insole board. Prior to injection molding, a stainless steel plate is inserted between the liner and the insole board at the forepart of the insole. The impact-resistant plastic layer is then injected molded between the liner and the insole board. The plastic layer overlaps the top and bottom faces of the plate and is anchored to the plastic layer through locking holes located at the rear margin of the plate.
The protective insole taught by Aleven is light in weight since a substantial portion of the steel plate in the conventional protective insole is replaced with lightweight plastic. However, numerous deficiencies are inherent in the Aleven insole. First, as the plastic only bonds with the rear margin of the stainless steel plate, the resulting flex zone may be too narrow to allow the wearer to walk comfortably. Second, as flexing is localized over a very narrow zone, at the region of greatest flexure, the bond between the plastic and the steel plate may separate prematurely, thereby exposing the bottom of the foot to the possibility of injury from sharp objects. Finally, Aleven teaches nothing about providing seamless protection for the toes and the underside of the foot.
Accordingly, there remains a need for a comfortable protective insert which is lightweight and durable, and which offers seamless protection for the toes and the underside of the foot.